Gray lava stone is the witness of the earth's violent heartbeat, which originates from the majestic power of the fiery core of the earth, and its color is cold, just like the dome of lead clouds, and like the dark gray cover of an ancient history book, which silently tells the vicissitudes of the sea of billions of years. The dense texture of the surface is the residue of boiling memories; the vague sense of touch lets the fingertips feel the after-temperature of the earth's eruption.